The sense of smell has long been used as a diagnostic tool by medical clinicians. Because of its subjectivity and the lack of correlative monitors, smell, as a diagnostic tool, has never achieved significant prominence in modern medicine. xe2x80x9cElectronic nosesxe2x80x9d or xe2x80x9celectronic olfactory sensorsxe2x80x9d have recently been developed to provide objective measurements and analysis of aromas. One particular xe2x80x9celectronic nosexe2x80x9d which has achieved some commercial success, primarily in the area of quality control and environmental monitoring in particular industries such as the beverage, flavor, perfume and certain aspects of the food industries, is manufactured by Aromascan, Inc. of Hollis, N.H. The Aromascan product uses changes in an electrical property (specifically, impedance or resistance) of sensors in a sensor array made of a layer of a semi-conducting organic polymer, when exposed to particles in a gas for aroma analysis. The Aromascan product is disclosed in U.S. Pat. No. 4,887,455 (Payne et al.), the disclosure of which is incorporated herein by reference. The use of the Aromascan product permits the characterization and digital representation of aromas for the measurement, recording and objective analysis of aromas. In this manner, the Aromascan product emulates the performance of the human nose with discrimination, sensitivity and, most importantly, objective reproducibility. Details concerning the structure and operation of the Aromascan product are available from Aromascan and the above-cited patent.
When using the Aromascan product, an aroma sample is exposed to the sensor and provides an aroma xe2x80x9cfingerprintxe2x80x9d which may be compared to another aroma finger print or other base data to provide a characterization of the sensed aroma. The Aromascan product outputs data regarding the aroma sample in the following formats:
1. A bar chart/histogram which shows the response of each sensor in the sensor array to the aroma presented to the array. Both the line pattern and the bar chart will be different for each odor thereby giving each odor a unique fingerprint.
2. Overlaid bar charts which highlight the average degree of differences between two samples at each individual sensor in the array.
3. 2-dimensional or 3-dimensional xe2x80x9cAromaMaps.xe2x80x9d The plural sensor data may be reduced to one point on a 2-D or 3-D plot or map which represent normalized histogram values. These plots allow for sample-to-sample comparisons. Samples which are similar to each other form populations or clusters on the map. Different aromas should fall within different clusters.
AromaMaps are one form of a xe2x80x9cmulti-dimensional mapxe2x80x9d for representing the sensor data and may be referred to generically as a principle component analysis (PCA) map. Another form of a multi-dimensional map which may be used for representing the sensor data is a Sammon map, such as shown in FIG. 5 of U.S. Pat. No. 5,807,701.
Two conventional sampling techniques for exposing an aroma to an electronic nose sensor include static headspace analysis and flow injection analysis. In static headspace analysis, a headspace above the sample is defined which becomes saturated with the odor. The odor is then pumped across the sensor. In flow injection analysis, a known gas is constantly pumped across the sensor. Next, a known concentration of the gas to be sampled is injected into the fluid stream before the sensor.
Electronic noses and methods of using electronic noses are further described in U.S. Pat. No. 5,675,070 (Gelperin); U.S. Pat. No. 5,697,326 (Mottram et al.); U.S. Pat. No. 5,788,833 (Lewis et al.); U.S. Pat. No. 5,807,701 (Payne et al.); and U.S. Pat. No. 5,891,398 (Lewis et al.), the disclosures of which are incorporated herein by reference.
U.S. Pat. No. 5,807,701 (Payne et al.), assigned to Aromascan PLC, discloses an in vitro method for identifying a microorganism, and particularly, vapors associated with the bacteria Staphylococcus aureus, Escherichia coli and Group A beta-haemolytic streptococci. In the method, the sample is in a Petri dish or like laboratory culture dish and undergoes culturing and growth before sampling occurs. A combination of static headspace analysis and flow injection analysis is used to perform the sampling.
U.S. Pat. No. 5,697,326 (Mottram et al.) discloses an examination device in the form of an open-top vessel which is used in conjunction with an electronic nose to sample odors emanating from the teat of a ruminant animal. The sampling is performed prior to milking to determine if the animal should be milked, cleaned or examined further. The patent also states that the examination device may be used to sample exhaled breath from the respiratory tract of a ruminant animal to determine selected conditions of the animal, such as oestrus (estrus) and ketosis. No data is presented to support these uses.
The diagnosis of pulmonary infections in mammals such as humans is a time-consuming, resource intensive process and sometimes inaccurate process. A chest x-ray does not necessarily provide an accurate indication of the presence or absence of an infection. Bacterial culture results typically take one to three days. During the test result waiting period, patients may be given powerful, often unneeded antibiotics which foster the growth of resistant bacteria.
Accordingly, there is an unmet need for a fast, accurate and inexpensive process for diagnosing pulmonary infections. The present invention fulfills this need.
Cerebrospinal fluid (CSF) is a clear fluid that circulates in the space surrounding the spinal cord and brain. CSF bathes, cushions and protects the spinal cord and brain. CSF flows through the skull and spine in the subarachnoid space.
The sinuses of a healthy patient contain mucus produced by sino-nasal mucosa and does not contain CSF. The sinuses of a patient who has a skull-base defect (either congenital, iatrogenic or trauma-induced) may contain CSF. In such patients, CSF may leak or drain through a skull-base defect into the sinuses and then into the nose. CSF may also drain directly into the nose through a skull-base defect at the olfactory cleft. Since sinus mucus and CSF are both clear fluids, a clinician cannot tell whether a CSF leak exists unless a patient ultimately tests positive for CSF.
In a patient suspected of having a CSF leak, sinus fluid is collected by gravity drip (e.g., the patient leans forward and nasal fluid drains out of the nostril into a vial), pledget sampling, aspiration or other means. A beta-2 transferrin enzyme assay is then conducted on the fluid sample to determine the presence of CSF. Although this test is very accurate, the test requires a relatively large amount of fluid. It is sometimes difficult to obtain a sufficiently large amount of fluid to conduct the test. Also, in many institutions, there can be a turnaround time of 24-48 hours for results. If a patient ultimately tests positive for CSF, the underlying condition or disease which caused the CSF leak may remain untreated unless other obvious signs of the condition, such as meningitis become apparent.
Accordingly, there is an unmet need for a fast, accurate and inexpensive process for detecting whether a fluid sample contains CSF, thereby differentiating CSF from other sinus-related fluids. There is also an unmet need for a testing process which does not require large quantities of fluid. The present invention also fulfills these needs.
The present invention provides a method of detecting the presence of a pathologic process in a lung of a mammal. In the method, a sample of exhaled gas collected from the lung of a mammal is applied to an electronic nose. The electronic nose analyzes the sample to determine whether a pathologic process is present in the lung of the mammal.